The trivia items below may give away important plot points.
In this movie, Shin Ha-kyun's character (Kang-woo) is killed by Song Kang-ho's character (Father Sang-hyun) by drowning. In "Sympathy for Mr. Vengeance" (2002), Shin Ha-kyun's character is also killed by Song Kang-ho's character by drowning. Both movies are directed by Park Chan-wook.
The climax of the book "Therese Raquin" differs from the film in that in the book, when the paralyzed Madame Raquin (Lady Ra) attempts to communicate to her guests that Therese (Tae-ju) and Laurent (Priest Sang) murdered her son Camille (Kang-woo) by spelling it out on the table with her fingers, she succeeds only in spelling the two names. The guests conclude that she is trying to tell them that Therese and Laurent are taking good care of her. At the very end of the book she is finally relieved of her agony by watching the two lovers poison themselves and die in front of her.